In the field of diagnostic and monitoring devices as used in the medical device industry, especially those used for analysing blood or other bodily fluid samples, it is often required for users to monitor biometrics such as the levels of certain chemicals, substances, or analytes present in their bloodstream. For instance, diabetics in particular must regularly monitor the concentrations of glucose in their blood in order to determine if they are in need of insulin. In order to respond effectively to an individual's needs to monitor blood sugar levels, diagnostic and monitoring devices and kits have been developed over the years to allow an individual to autonomously determine the concentration of glucose in their bloodstream, in order to better anticipate the onset of hyperglycaemia or hypoglycaemia and take preventative action as necessary. The existence of such diagnostic and monitoring devices places less strain on the healthcare system at large, as patients are able to administer insulin in their own home and without having to do so in the presence of a medical professional.
Typically the patient will, using a lancing device, perform a finger stick to extract a small drop of blood from a finger or alternative site. An electrochemical test device, which is often a strip, is then inserted into a diagnostic/monitoring meter, and the sample is applied on the test strip. Through capillary action, the sample flows across a measurement chamber of the device and into contact with one or more electrodes or similar conductive elements coated with sensing chemistry for interacting with a particular analyte or other specific chemical (for example glucose) in the blood sample. The magnitude of the reaction is dependent on the concentration of the analyte in the blood sample. The meter may detect the current generated by the reaction of the reagent with the analyte, and the result can be displayed to the user.
It is important that the reading output by a meter can be relied upon so that if necessary appropriate action may be taken. If the reading is erroneous and the user acts upon the erroneous reading, any action taken (e.g. the administration of insulin) could be detrimental to the user's health. Erroneous readings can arise not only if the test strip is damaged (which could for example affect the flow of the fluid sample across the measurement chamber), but also if the meter itself is damaged.
To address this issue, control solutions having known concentrations of one or more analytes have been developed. The control solution is applied to a test strip and tested using the meter, usually when a new batch of strips is opened. Because the concentration of the analyte of interest in the control solution is known, the meter reading is expected to fall within a predetermined range (usually indicated on the vial containing the strips). If the reading passes this test then the user is given the confidence to proceed with a blood-analyte measurement. As an increased precaution, governmental regulatory bodies such as the FDA generally require that in order to be fit for distribution a meter must satisfy a test of multiple control solutions with different concentrations of analyte. Control solutions are important and useful for verifying the integrity of one or more strips as well as the calibration of the meter itself. However, unless a relatively simple measurement/algorithm is used with the control solution (e.g. a single current reading at a fixed time, and a slope and intercept to convert the current value to an analyte reading), control solutions generally do not allow for verification of the integrity of the meter hardware and software responsible for carrying out an analyte measurement when a non-control solution is being tested. Whilst this could be addressed by developing control solutions that mimic the behaviour of blood (or whatever non-control solution is being tested), such development could not be arrived at without significant time and expense given that blood is a complex matrix sample containing many constituents not present in simple control solutions (such as blood cells).
There therefore remains a need in the art to carry out a check of the meter components responsible for carrying out an analyte measurement when a non-control solution (e.g. blood) is being tested, without having to develop blood-mimicking control solutions. The present disclosure seeks to address this need.